Coastal batteries can be built around full ship-standard turrets

Would shallow shore mountings really help preserve the skills needed for deep shipboard turrets?

Only if the coastal bunker is deliberately built deep enough to accept the full ship-standard turret and ammunition-handling system.

An ordinary coastal mounting would be shallower than a naval turret. If the purpose is to sustain ship-turret production, however, the bunker should be designed around the complete ship-standard mechanism. The working cage extends through several deck levels, with ammunition handling and supporting structure reaching farther below. Excavation, concrete, and labor make the battery more expensive, but they preserve the exact machinery and skills the program is meant to retain.